The scale of the climate emergency makes it a topic of global importance – one on which all major powers must have a position. It is clearly appropriate to discuss the issue of energy transition at the European level; Commission President Von der Leyen herself has made it a priority, with the announcement of the creation of a European energy transition fund. France’s 2015 “Energy transition for green growth” Act has charted the course for a new French energy model within a European framework. Pursuant to this legislation, since January 1, 2020 (2018 for RATP), half of all new buses must be low-emission vehicles; they must all be by 2025. How can energy transition be successfully achieved whilst also maintaining high service levels and controlling costs? What policies are our German, Italian, and Spanish neighbours implementing in this respect? What obligations do they have? What progress have they made in the use of non-diesel alternatives? What solutions are being favoured, and why?